From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 28782 invoked by alias); 21 Aug 2011 09:19:48 -0000 Received: (qmail 28774 invoked by uid 22791); 21 Aug 2011 09:19:47 -0000 X-SWARE-Spam-Status: No, hits=-2.9 required=5.0 tests=ALL_TRUSTED,AWL,BAYES_00 X-Spam-Check-By: sourceware.org Received: from localhost (HELO gcc.gnu.org) (127.0.0.1) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Sun, 21 Aug 2011 09:19:34 +0000 From: "rguenth at gcc dot gnu.org" To: gcc-bugs@gcc.gnu.org Subject: [Bug target/50131] Optimize x = -1 with "or" for -O Date: Sun, 21 Aug 2011 09:20:00 -0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: target X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: rguenth at gcc dot gnu.org X-Bugzilla-Status: UNCONFIRMED X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated Content-Type: text/plain; charset="UTF-8" MIME-Version: 1.0 Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-bugs-owner@gcc.gnu.org X-SW-Source: 2011-08/txt/msg01749.txt.bz2 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50131 --- Comment #4 from Richard Guenther 2011-08-21 09:19:28 UTC --- I'm sure or $-1,reg doesn't avoid the data dependence on reg and may even result in hitting partial reg stall issues. Surely xor reg,reg; not reg might be another alternative?